﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            double r;
            double mj;
            Console.WriteLine("请输入有圆的半径：");
            r = double.Parse(System.Console.ReadLine());
            mj = r*r * 3.14;
            Console.WriteLine("圆的面积为"+mj);
            Console.ReadKey();
            return;
        }
    }
}
